Iron metabolism disorders and hemolytic anemias

Kleber Y. Fertrin, MD, PhDAssistant Professor, University of Washington

Director, Hemolytic Anemias and Iron Disorders Program kleber@uw.edu

ABIM Hematology exam blueprint

2

ABIM Hematology exam blueprint

3

MULTIPLICATION

Stages of erythropoiesis

BFU-E CFU-EStem cell

Proerythrobasophilic

polychromatophilic

orthochromatic

reticulocyte

mature erythrocyteSCF, IL-3, EPOMedullary stroma

DIFFERENTIATION

HEMOGLOBINIZATIONIron

Normal MCV 80-99fL

High MCV >99fL

Low MCV <80fL

Anemias of the hemoglobinization stage (microcytic, MCV<80fL)

Lack of a component of hemoglobin1. Iron deficiency

• Absolute: iron deficiency anemia• Functional: anemia of inflammation /chronic disease

2. Globin deficiency• Thalassemias (see other lecture)

3. Heme deficiency• Hereditary sideroblastic anemia

• ALA synthase mutation (ALAS2 gene)• Chronic lead poisoning

• ALA synthase inhibition

Physiology of iron metabolismDietary iron

DUODENUM

LIVERMACROPHAGES1000mg Fe

600mg Fe

1800mg Fe

Absorption 1-2mg/day

3mg Fe

Plasmatransferrin

ERYTHROCYTES

LOSSES1-2mg Fe

BONE MARROW300mg Fe

Menstrual bleedingIntestinal epithelial turnover

Common “iron studies”Test Usual reference ranges

Serum ferritin(mcg/L)

20-200 (female)30-300 (male)

Serum iron(mcg/dL)

60-180

Total iron binding capacity(mcg/dL)

270-535 (female)250-460 (male)

Serum transferrin(mg/dL)

192-382 (female)180-329 (male)

Transferrin saturation (TSAT)(Serum iron/TIBC)

(%)

20-45 (female)20-50 (male)

Diagnosis of iron deficiency anemia

• Anemia = low RBC production: low Hb, Hct, and RBCs• Beta thal trait has normal or elevated RBCs

• Hypoproliferative: reticulocytes are normal or low • High reticulocytes (>100k) – think acute bleeding or

hemolysis!• Biochemical evidence of iron deficiency

• Ferritin <30mcg/L (men) or <20mcg/L (women)• Low serum iron with high TIBC = low transferrin saturation

<20% (typically <16%)• Work up for causes

Causes of iron deficiency

• Always investigate bleeding (GI, Gyn, epistaxis, hematuria)• Malabsorption

• Surgical (gastric bypass, resections…)• Inflammatory bowel diseases• Parasites (hookworm)• Atrophic gastritis• Prolonged use of medications (e.g. PPI)

• Vegetarian/vegan diet DOES NOT cause iron deficiency by itself

Treat or control the underlying cause!

Treatment of iron deficiency anemia - 1

Goals of iron supplementation:1. Normalize CBC (first phase, takes about 4-6 months)

Hb>12g/dL women, Hb>13g/dL men AND Normal MCV (>80fL) and MCH (>28pg)

2. Normalize iron stores (usually 3-4 more extra months) Ferritin >20ug/L for women, >30ug/L for men AND Transferrin saturation > 20%

Oral iron: ferrous sulfate, fumarate, gluconate• First line of therapy• Single, lower (100-150mg elemental iron) dose qod favored (e.g. ferrous

sulfate 325mg 2 tab qod)• Side effects: GI symptoms (>50%), dark stools

Treatment of iron deficiency anemia - 2

Intravenous iron• Formulations: Iron sucrose, low molecular weight iron dextran, iron gluconate, ferric carboxymaltose, ferumoxytol, iron isomaltoside• Consider if :

Intolerance/failure to oral iron Malabsorption (e.g gastric bypass, IBD) CKD

• Side effects: Anaphylaxis: RARE these days, mostly associated with

HIGH-molecular weight dextran (discontinued); Skin hyperpigmentation Hypophosphatemia (ferric carboxymaltose, isomaltoside)

Gan & Orringer, Dermatol Surg 2015

MACROPHAGES

Dietary iron DUODENUM

LIVER

Absorption

Plasma transferrin RBCs

LOSSES

BONE MARROW

Hepcidin

ANEMIA OFINFLAMMATION

Inflammation (IL-1, IL-6)Infection (LPS)

Pathophysiology of anemia of inflammation

Inflammation induces hepcidin

FeFe

Fe

FeFe

Fe FeFe Fe

Fe

Fe

FeFe

Fe Fe

Fe

Hepcidin internalizes and degrades ferroportin

Iron (Fe) gets trapped inside cells

Diagnosis of anemia of inflammation

• History of underlying chronic disease:• Inflammatory: RA, SLE, IBD, Castleman’s disease• Infections: Tb, osteomyelitis, endocarditis• Malignancy: lymphoma and other hematologic• Other chronic conditions: CHF, COPD

• Lab findings: Mild to moderate hypoproliferative N/N anemia (occasionally

microcytic) Low serum iron with low TSAT <20% Normal to increased serum ferritin (>100 mcg/L) May have elevated CRP>5 mg/L but not required Investigational: hepcidin levels

Management of anemia of inflammation

• Treatment of the underlying disorder is usually best;

• Iron supplementation: usually NOT indicated unless combined iron deficiency exists (e.g. if ferritin <100ug/L), or if patient on ESA for CKD;

• Erythropoiesis-stimulating agents: consider if CKD-associated, or in some patients undergoing chemotherapy for malignancy

• Transfusions: only if symptomatic, life-threatening anemia• Investigational: hepcidin blockers

Pathophysiology of Hereditary Hemochromatoses

Uncontrolled iron absorption due to hyperactivity of ferroportin (mostly dueto hepcidin deficiency)

159/2/2020

Adapted from Brissot et al., Nat Rev Dis Primers 2018

Ferroportin

(SLC40A1)

Hemochromatosis – Clinical featuresClassical HH • type 1, HFE mutation

(Northern Europe origin)• type 3, TFR2 mutation

(rare, may have earlieronset)

• type 4B, SLC40A1mutation (gain-of-functionferroportin)

Juvenile HH • type 2A, hemojuvelin

mutation• type 2B, hepcidin

mutation (extremely rare)

169/2/2020

Brissot et al., Nat Rev Dis Primers 2018

Hemochromatosis - DiagnosisLabs: No anemiahigh ferritin AND TSAT>45%

• Northern European ascent: start with HFE testing• HFE C282Y/C282Y or heterozygote C282Y/H63D: diagnosis of HH• HFE H63D/H63D: diagnosis is debatable; low penetrance• Other genotypes: non-diagnostic, pursue other causes

• No obvious Northern European ascent: start with MRI T2* to confirm ironoverload; if positive for liver iron overload:• If age<30, consider testing for HAMP, HJV, TFR2 genes• If age>30, consider testing for HFE, TFR2, SLC40A1 genes

179/2/2020

Hemochromatosis - treatment• Avoid iron supplements and alcohol;

• Tea, coffee comsumption and use of PPI can decrease absorption• No need to follow iron-poor diet

• Phlebotomy – GOAL: ferritin 50-100mcg/L Induction: 400-500mL weekly provided Hb>11g/dL Maintenance : maximum interval to keep ferritin at goal Blood donation: acceptable in some countries

• Erythrocytapheresis: allows faster iron removal; higher cost; side effectsof procedure (hypocalcemia, longer procedure)

• Iron chelation: low dose deferasirox may be used for those intolerant tophlebotomy

• Liver transplantation may be required and is curative

189/2/2020

Hemolytic anemiasCAUSES- Malaria (and other infections- Clostridium, Babesia)- Medications (drug-induced or oxidative)- Microangiopathies- Motherhood (think antibodies: hemolytic disease of the newborn;

transfusion reactions; don’t forget autoimmune)- Mutations

- Acquired mutation PIG-A: paroxysmal nocturnal hemoglobinuria- Congenital (think COMPONENTS OF A RED CELL):

- Hemoglobin (other lecture)- Membrane: HS, elliptocytosis, stomatocystosis, xerocytosis...- Enzyme: G6PDD, PKD

199/2/2020

Red cell membranopathies - HS

• Hereditary spherocytosis is the most common inherited hemolytic anemia due to membrane defects (1/3,000, all racial groups)

• AD in 75%; mutation in ankyrin, spectrin or band 3 (VERTICAL linkages); may occur de novo;

• Family history of gallstone and/or splenectomy; • Clinical features: hemolysis with high MCHC; negative

DAT; may have hypersplenism• Diagnosis:

• osmotic fragility test with right shift of the curve; reduced fluorescence with eosin-5’-maleimide (flow cytometry)

• Treatment: splenectomy is curative

Na & Mohandas, Br J Haematol 2008;141(3):367-375op

Other red cell membranopathies

1. Hereditary elliptocytosis• AD, more common in malaria endemic regions• Alpha spectrin (65%), beta spectrin or protein 4.1R mutations (LATERAL

linkages)• Hereditary pyropoikilocytosis – homozygous or compound heterozygous

spectrin mutations causing severe form of HE2. Southeast Asian Ovalocytosis: mild or no hemolysis with ovalocytes causes by

unique 27bp deletion in band 33. Hereditary stomatocytoses: AD defects in volume control

1. xerocytosis (compensated hemolysis, macrocytosis, <10% stomatocytes)2. overhydrated stomatocytosis (frank stomatocytosis with hemolytic anemia)

Brissot et al., Nat Rev Dis Primers 2018

Red cell enzymopathies

• Glucose-6-phosphate dehydrogenase (G6PD) deficiency • Recessive X-linked inheritance• Variable phenotype: mostly episodic hemolytic crises; may present as chronic

non-spherocytic hemolytic anemia• Diagnosis: Heinz bodies during hemolysis; low G6PD activity outside of

hemolytic episode (false normal G6PD with reticulocytosis)• Triggers: infections, medications (dapsone, primaquine)

• Pyruvate kinase deficiency (PKD)• Most common defect of the glycolytic pathway; AR• Chronic non-spherocytic anemia with variable severity• Macrocytosis and extreme reticulocytosis (>50%) postsplenectomy• May develop spontaneous iron overload

Autoimmune hemolytic anemias

• Acquired hemolytic conditions with production of abnormal antibodies reacting against red cell epitopes

• Positive hemolytic markers (increase in reticulocyted, LDH, indirect bilirubin, with low haptoglobin)

• Direct antiglobulin test: detects immunoglobulins and complement bound to red blood cells (“direct Coombs’ test)

• IgG+: warm AIHA (typically with spherocytes in peripheral blood smear)• Complement (C3b) and/or IgM: cold AIHA• IgG and C3b: mixed AIHA

Warm autoimmune hemolytic anemia - management

• Transfusions: if severe anemia (Hb<6), instability; beware of history of alloimmunization; failure to respond may indicate IVIg.

• First line of therapy is glucocorticosteroids (e.g. prednisone 1-2mg/kg/day with taper after 2-3 weeks if response)

• Second line therapy: • Rituximab (may be used as first line)• Splenectomy (often third line)• Other immunosuppressants

• MMF, cyclophosphamide, azathioprine, cyclosporine• sirolimus – may be preferred in children/young adults with ALPS

Cold agglutinin disease – clinical features

• Cold-induced symptoms• Acrocyanosis• Livedo reticularis / skin ulcers• Raynaud’s phenomenon• Dysphagia or pain upon ingesting cold food

• Extravascular hemolytic anemia (may be precipitated by cold or infections)• Spurious macrocytosis• In vitro agglutination

• Venous thromboembolism

Cold agglutinin disease – diagnosis

• Evidence of hemolysis• DAT positive for complement (C3d)• Cold agglutinin titer 1:64 or higher at 4oC

• IgM with specificity anti-I (often linked to Mycoplasma) or anti-i (often linked to mononucleosis)

Classification:• Primary CAD: typically associated with a monoclonal IgM kappa not

meeting criteria for a lymphoproliferative disorder (MGUS)• Secondary CAD: infections, autoimmune disorder, or lymphoid malignancy

Cold agglutinin disease – treatment

• Cold avoidance• Transfusions: avoid cooling down patient’s sample for crossmatch; use of

blood warmers• Plasmapheresis and IVIg can be used as temporizing measures in severe

cases• For secondary CAD, treatment of the underlying disorder is appropriate • For primary CAD:

• Consider first line with rituximab containing regimen (e.g. rituximab + bendamustine); may associated with fludarabine, prednisone, interferon, or monotherapy;

• Alternative regimen: bortezomib.• Investigational: anti-complement therapies (sutimlimab)

Drug-induced hemolysis

• Most common: diclofenac, ceftriaxone, piperacillin, oxaliplatin• Mechanisms:

• DAT-positive (IgG and/or C3)• Hapten formation: penicillin, ceftriaxone• Drug-independent: methyldopa

• Oxidative hemolysis: primaquine, dapsone, phenazopyridine – worse if associated with G6PD deficiency

• Methemoglobinemia: anesthetics, nitrites• Drug-induced thrombotic microangiopathy: quinine, Bactrim, oxaliplatin,

gemcitabine, mitomycin, bevacizumab, sunitinib, proteasome inhibitors, quetiapine, cyclosporine, tacrolimus, sirolimus

• Other mechanisms: ribavirin, artesunate (for malaria), interferon alpha

Paroxysmal nocturnal hemoglobinuria (PNH)

• Acquired clonal disorder with PIGA gene mutation loss of GPI-anchored proteins susceptibility to complement destruction

1. Classical PNH• Pancytopenia• Non-autoimmune hemolytic anemia

• Fatigue, jaundice, hemoglobinuria• Smooth muscle dystonia: dysphagia, erectile dysfunction

• Hemostasis activation: venous thromboembolic events in unusual vessel beds • Abdominal VTE (Budd-Chiari syndrome)• Upper extremity• Venous sinuses

2. PNH clone in the context of another hematologic disorders (aplastic anemia, MDS, PMF)

Paroxysmal nocturnal hemoglobinuria

• Diagnosis: Peripheral blood flow cytometry • lack of at least 2 GPI-anchored proteins in

at least 2 different lineages • Treatment:

• Support for anemia: folic acid, iron supplementation if iron deficient due to hemoglobinuria, transfusions

• Symptomatic disease: complement inhibitors eculizumab or ravilizumab

• prophylaxis for meningococcal infections

• Allogeneic hematopoietic cell transplant for AA/MDS, refractory disease, or severe disease without access to anti-complement therapy

Copyright © 2020 American Society of Hematology.

Microangiopathic hemolytic anemias1. Thrombotic microangiopathy: TTP, HUS2. Systemic conditions:

• DIC• Pre-eclampsia / HELLP syndrome• Malignancy• Scleroderma renal crisis• Malignant hypertension• Antiphospholipid syndrome

3. Localized hemolysis:• Hemangioma (Kasabach-Merritt syndrome)• TIPS• Malfunctioning cardiac valve or assist device• March hemoglobinuria (includes extreme running, bongo drumming)

31

Copyright © 2020 American Society of Hematology. Image Bank.

9/2/2020 32

Educational resources• American Society of Hematology Self-Assessment Program 6th Ed.

(ASH SAP)

• ASH Pocket Guides (download from App store)

• Hematology/Oncology question bank http://hemeoncquestions.com/

• Hematology-Oncology board review questionswww.turner-white.com/brm/bonco.htm

THANK YOU